Composite armor plate and method for using the same

ABSTRACT

The invention provides an armor plate for absorbing and dissipating kinetic energy from armor piercing 7.62 mm projectiles having a projectile length of from 32.8 mm to 37 mm, the armor plate comprising a plurality of ceramic pellets and a solidified material, each ceramic pellet having a body portion and a convexly curved end portion, each body portion having two opposite ends, an axis passing through each end and a substantially constant cross-section along the axis, and each convexly curved end portion extending from an end of the corresponding body portion, each body portion having a body portion length along the axis between the two ends, the ceramic pellets being embedded in the solidified material so that the solidified material retains the ceramic pellets in a ceramic pellet layer which is one pellet thick with the convexly curved end portions lying at or adjacent an impact receiving side of the armor plate, wherein the ceramic pellet layer is the only layer of ceramic pellets in the armor plate, wherein the ceramic pellet layer has an edge extending therearound formed by a subset of the ceramic pellets, wherein the ceramic pellets are arranged so that the body portion of substantially each pellet, other than of the pellets of the subset, lies in contact with or closely adjacent to the respective body portions of six neighboring ones of the ceramic pellets so that there are a plurality of valleys extending through the ceramic pellet layer with each valley being bordered by three adjacent ceramic pellets, wherein substantially each valley has a shape and size such that the diameter of the largest imaginary circle that will fit into the each valley between the neighboring body portions and substantially perpendicularly to the neighboring axes is from 1.96 mm to 3.7 mm, and wherein each body portion length is from 5.57 mm to 10.73 mm.

The invention relates to an armor plate for absorbing and dissipatingkinetic energy from armor piercing 7.62 mm projectiles having aprojectile length of from 32.8 mm to 37 mm. The invention also relatesto a method of manufacturing an armor plate for absorbing anddissipating kinetic energy from armor piercing 7.62 mm projectileshaving a predetermined projectile length. The invention further relatesto a method of using an armor plate.

More specifically, the present invention relates to composite ceramicarmor and to the tailoring thereof for protecting against 7.62 mmcaliber armor-piercing projectiles having a predetermined projectilelength. Preferably, armor plates tailored to protect against a specific7.62 mm caliber armor-piercing projectile will have multi-hit protectioncapability for shattering and preventing penetration by a plurality ofthe 7.62 mm armor piercing projectiles.

The projectile length is the length of the projectile itself and not thelength of the complete bullet including the casing.

The term “multi-hit” as used herein relates to the property of the platefor shattering three projectiles fired sequentially at a triangular areaof said panel, the sides of said triangle being about 6-7 cm each,

According to a first aspect of the invention, there is provided an armorplate for absorbing and dissipating kinetic energy from armor piercing7.62 mm projectiles having a projectile length of from 32.8 mm to 37 mm,the armor plate comprising a plurality of ceramic pellets and asolidified material, each ceramic pellet having a body portion and aconvexly curved end portion, each body portion having two opposite ends,an axis passing through each end and a substantially constantcross-section along said axis, and each convexly curved end portionextending from an end of the corresponding body portion, each bodyportion having a body portion length along said axis between the twoends, the ceramic pellets being embedded in the solidified material sothat the solidified material retains the ceramic pellets in a ceramicpellet layer which is one pellet thick with said convexly curved endportions lying at or adjacent an impact receiving side of the armorplate, wherein the ceramic pellet layer is the only layer of ceramicpellets in the armor plate, wherein the ceramic pellet layer has an edgeextending therearound formed by a subset of said ceramic pellets,wherein said ceramic pellets are arranged so that the body portion ofsubstantially each pellet, other than of the pellets of said subset,lies in contact with or closely adjacent to the respective body portionsof six neighboring ones of the ceramic pellets so that there are aplurality of valleys extending through the ceramic pellet layer witheach valley being bordered by three adjacent ceramic pellets, whereinsubstantially each valley has a shape and size such that the diameter ofthe largest imaginary circle that will fit into said each valley betweenthe neighboring body portions and substantially perpendicularly to theneighboring axes is from 1.96 mm to 3.70 mm, and in that each bodyportion length is from 5.57 mm to 10.73 mm.

For the first aspect of the invention, the diameter of the largestimaginary circle (as defined above) is preferably chosen to be from 6%to 10% of the length of the projectile against which the armor plate istailored to protect, while each body portion length is preferably chosento be from 17% to 29% of the projectile length. Hence, for example, whenthe projectile length of the projectile to be protected against is from32.8 mm to 34.0 mm, the diameter of the largest imaginary circle willpreferably be from 1.96 mm to 3.40 mm and each body portion length willpreferably be from 5.57 mm to 9.86 mm. When the projectile length of theprojectile to be protected against is from 34.0 mm to 35.0 mm, thediameter of the largest imaginary circle will preferably be from 2.04 mmto 3.50 mm and each body portion length will preferably be from 5.78 mmto 10.15 mm. When the projectile length of the projectile to beprotected against is from 35.0 mm to 36.0 mm, the diameter of thelargest imaginary circle will preferably be from 2.10 mm to 3.60 mm andeach body portion length will preferably be from 5.95 mm to 10.44 mm.When the projectile length of the projectile to be protected against isfrom 36.0 mm to 37.0 mm, the diameter of the largest imaginary circlewill preferably be from 2.16 mm to 3.70 mm and each body portion lengthwill preferably be from 6.12 mm to 10.73 mm. Values for the largestimaginary circle and for the body portion length can be calculated as apercentage of the projectile length, as discussed above, for anyspecific projectile length or for any range of projectile lengths. Forexample, values can be calculated for each projectile length in therange from 32.8 mm to 37.0 mm.

According to a second aspect of the invention, there is provided amethod of manufacturing an armor plate for absorbing and dissipatingkinetic energy from armor piercing 7.62 mm projectiles having apredetermined projectile length, comprising:

Selecting said projectile length of said armor piercing 7.62 mmprojectiles for which the kinetic energy is to be absorbed anddissipated by said armor plate;

Manufacturing the armor plate wherein the armor plate comprises aplurality of ceramic pellets and a solidified material, each ceramicpellet having a body portion and a convexly curved end portion, eachbody portion having two opposite ends, an axis passing through each endand a substantially constant cross-section along said axis, and eachconvexly curved end portion extending from an end of the correspondingbody portion, each body portion having a body portion length along saidaxis between the two ends, the ceramic pellets being embedded in thesolidified material so that the solidified material retains the ceramicpellets in a ceramic pellet layer which is one pellet thick with saidconvexly curved end portions lying at or adjacent an impact receivingside of the armor plate, wherein the ceramic pellet layer is the onlylayer of ceramic pellets in the armor plate, wherein said ceramic pelletlayer has an edge extending therearound formed by a subset of saidceramic pellets, wherein said ceramic pellets are arranged so that thebody portion of substantially each pellet, other than of the pellets ofsaid subset, lies in contact with or closely adjacent to the respectivebody portions of six neighboring ones of the ceramic pellets so thatthere are a plurality of valleys extending through the ceramic pelletlayer with each valley being bordered by three adjacent ceramic pellets;

Wherein said manufacture includes selecting the size and shape of theceramic pellets according to the predetermined projectile length so thatsubstantially each valley has a shape and size such that the diameter ofthe largest imaginary circle that will fit into said each valley betweenthe neighboring body portions and substantially perpendicularly to theneighboring axes is from 6% to 10% of the predetermined projectilelength, and wherein each body portion length is from 17% to 29% of thepredetermined projectile length.

According to a third aspect of the invention there is provided a methodof using an armor plate, said method comprising:

Providing an armor plate comprising a plurality of ceramic pellets and asolidified material, each ceramic pellet having a body portion and aconvexly curved end portion, each body portion having two opposite ends,an axis passing through each end and a substantially constantcross-section along said axis, and each convexly curved end portionextending from an end of the corresponding body portion, each bodyportion having a body portion length along said axis between the twoends, the ceramic pellets being embedded in the solidified material sothat the solidified material retains the ceramic pellets in a ceramicpellet layer which is one pellet thick with said convexly curved endportions lying at or adjacent an impact receiving side of the armorplate, wherein the ceramic pellet layer is the only layer of ceramicpellets in the armor plate, wherein said ceramic pellet layer has anedge extending therearound formed by a subset of said ceramic pellets,wherein said ceramic pellets are arranged so that the body portion ofsubstantially each pellet, other than of the pellets of said subset,lies in contact with or closely adjacent to the respective body portionsof six neighboring ones of the ceramic pellets so that there are aplurality of valleys extending through the ceramic pellet layer witheach valley being bordered by three adjacent ceramic pellets;

Using said composite armor plate for absorbing and dissipating kineticenergy from armor piercing 7.62 mm projectiles having a predeterminedprojectile length; and

Wherein substantially each valley has a shape and size such that thediameter of the largest imaginary circle that will fit into said eachvalley between the neighboring body portions and substantiallyperpendicularly to the neighboring axes is from 6% to 10% of thepredetermined projectile length, and

wherein each body portion length is from 17% to 29% of the predeterminedprojectile length.

The projectile will generally be shattered by the armor plate to formprojectile fragments.

Preferably, for any aspect of the invention, the ceramic pellets aredirectly bound by the solidified material. Hence there is no coating orthe like interposed between the ceramic pellets and the solidifiedmaterial.

Each body portion preferably has a shape that is symetrical about itsaxis or symetrical about a plane that is intersected by the axis. Onepreferred shape for the body portion is a cylinder (that is to say aright circular cylinder). Another preferred shape for the body portionis a prism of generally hexagonal cross-section with rounded edgesbetween each adjacent pair of axially extending faces. A generallyhexagonal prism of this type is shown in EP1,521,051.

Preferably, the shape and arrangement of the body portions is such thateach valley is surrounded by convexly curved lateral portions of theadjacent ceramic pellets. In other words, each lateral portion projectsinto the valley. Hence when the body portion is cylindrical, the valleyswill be surrounded by portions of the cylindrical surfaces. When thebody portions are hexagonal prisms with rounded edges as discussedabove, each valley will be surrounded by three convex rounded edges.

The convexly curved end face is preferably a segment of a sphere.

In general, both the solidified material and the armor plate will beslightly flexible. In this case, the terms “elastic” and “flexible”relate to the fact that the plates are bent when a load is appliedthereto and more specifically, the plates slightly flex with eachprojectile impact thereby augmenting the buttressing affect of adjacentpellets to the pellet being impacted or to the valley being entered bythe projectile, however upon release of said load, or at the end of thedissipation of the kinetic energy from the impacting high-velocityprojectile, the plate tends to return to its original shape, or close toits original shape with the exception of holes which might be formed asa result of the mutual destruction of a projectile and an arrestingpellet or pellets.

When the armor piercing projectile to be protected against has atungsten carbide core, the diameter of the largest imaginary circle ispreferably from 7% to 9% of the predetermined projectile length. Alsofor projectiles of this type each body portion length is preferably from22% to 29% of the predetermined projectile length.

For other projectiles, each body portion length is preferably from 19%to 24% of the predetermined projectile length.

Preferably, the ceramic pellets are substantially internal within thesolidified material and the outer faces of the armor plate aresubstantially formed by the solidified material.

As will be realized, when preparing the composite armor plate of thepresent invention, said pellets do not necessarily have to be completelycovered on both sides by said solidified material, and the term internalis intended to denote that the pellets are either completely or almostcompletely covered by said solidified material, wherein outer facesurfaces of the plate are formed from the solidified material, the platehaving an outer impact receiving face, at which face each pellet iseither covered by the solidified material, touches said solidifiedmaterial which forms surfaces of said outer impact receiving face or,not being completely covered by said solidified material whichconstitutes surfaces of said outer impact receiving face, bulgesslightly therefrom.

Preferably, the body portion of each ceramic pellets has a maximumcross-sectional dimension of greater than 13 mm, and more preferablybetween 14 mm and 20 mm. The maximum cross-sectional dimension is thelongest straight line intersecting the cross-sectional shape. Hence,when the body portion is cylindrical, the maximum cross-sectionaldimension is a diameter.

Preferably, each ceramic pellet has an overall length along its axis ofbetween 11.6 mm and 17 mm.

Preferably, the diameter of said largest imaginary circle is no greaterthan 3 mm.

When the plate is flat, the axes of the ceramic pellets will begenerally parallel to one another. However, curved plates can also beformed in which case the axes will be angled relative to one anotherdependent on the curvature of the plate.

Preferably the ceramic pellets in an armor plate will have substantiallythe same shape and size as one another. Even when the ceramic pelletsare the same size and shape as one another, the valleys can vary in sizedue to irregularities in the positions of the pellets in the plate.

In accordance with a fourth aspect of the invention, a multi-layeredarmor panel comprises an armor plate according to the first aspect ofthe invention or made in accordance with the second aspect of theinvention, said armor plate forming an outer layer for deforming andshattering into fragments an impacting high-velocity armor piercingprojectile, and a second layer positioned inwardly of and adjacent tothe armor plate, the second layer comprising a material that is softerthan the ceramic pellets and the second layer capturing the fragmentsand absorbing the remaining kinetic material from the fragments.

Preferably, the second layer is made of: polyethylene with an ultra highmolecular weight; aramid; aluminium; steel; titanium; or reinforcedfiberglass. In addition a third layer positioned inwardly (that is tosay on the opposite side of the second layer as compared to the armorplate) of the second layer and made of aluminium may be provided.

The present invention is a modification of the inventions described inU.S. Pat. Nos. 5,763,813; 5,972,819; 6,289,781; 6,112,635; 6,203,908;and 6,408,734,

EP 1,521,051 and in WO-A-9815796 the relevant teachings of which areincorporated herein by reference,

-   In U.S. Pat. No. 5,763,813 there is described and claimed a    composite armor material for absorbing and dissipating kinetic    energy from high velocity, armor-piercing projectiles, comprising a    panel consisting essentially of a single internal layer of high    density ceramic pellets said pellets having an Al₂O₃ content of at    least 93% and a specific gravity of at least 2.5 and retained in    panel form by a solidified material which is elastic at a    temperature below 250° C.; the majority of said pellets each having    a part of a major axis of a length of in the range of about 3-12 mm,    and being bound by said solidified material in plurality of    superposed rows, wherein a majority of each of said pellets is in    contact with at least 4 adjacent pellets, the weight of said panel    does not exceed 45 kg m².

In U.S. Pat. No. 6,112,635 there is described and claimed a compositearmor plate for absorbing and dissipating kinetic energy from highvelocity, armor-piercing projectiles, said plate consisting essentiallyof a single internal layer of high density ceramic pellets which aredirectly bound and retained in plate form by a solidified material suchthat the pellets are bound in a plurality of adjacent rows, wherein thepellets have an Al₂O₃ content of at least 93% and a specific gravity ofat least 2.5, the majority of the pellets each have at least one axis ofat least 12 mm length said one axis of substantially all of said pelletsbeing in substantial parallel orientation with each other andsubstantially perpendicular to an adjacent surface of said plate andwherein a majority of each of said pellets is in direct contact with 6adjacent pellets, and said solidified material and said plate areelastic.

In WO-A-9815796 corresponding to U.S. Pat. No. 5,972,819, there isdescribed and claimed a ceramic body for deployment in a composite armorpanel, said body being substantially cylindrical in shape, with at leastone convexly curved end face, wherein the ratio D/R between the diameterD of said cylindrical body and the radius R of curvature of said atleast one convexly curved end face is at least 0.64:1.

In U.S. Pat. No. 6,289,781 there is described and claimed a compositearmor plate for absorbing and dissipating kinetic energy from highvelocity projectiles, said plate comprising a single internal layer ofpellets which are directly bound and retained in plate form by asolidified material such that the pellets are bound in a plurality ofadjacent rows, characterized in that the pellets have a specific gravityof at least 2 and are made of a material selected from the groupconsisting of glass, sintered refractory material, ceramic materialwhich does not contain aluminum oxide and ceramic material having analuminum oxide content of not more than 80%, the majority of the pelletseach have at least one axis of at least 3 mm length and are bound bysaid solidified material in said single internal layer of adjacent rowssuch that each of a majority of said pellets is in direct contact withat least six adjacent pellets in the same layer to provide mutuallateral confinement therebetween, said pellets each have a substantiallyregular geometric form and said solidified material and said plate areelastic.

In U.S. Pat. No. 6,408,734 there is described and claimed a compositearmor plate for absorbing and dissipating kinetic energy from highvelocity, armor-piercing projectiles, as well as from soft-nosedprojectiles, said plate comprising a single internal layer of highdensity ceramic pellets, characterized in that said pellets are arrangedin a single layer of adjacent rows and columns, wherein a majority ofeach of said pellets is in direct contact with at least four adjacentpellets and each of said pellets are substantially cylindrical in shapewith at least one convexly-curved end face, further characterized inthat spaces formed between said adjacent cylindrical pellets are filledwith a material for preventing the flow of soft metal from impactingprojectiles through said spaces, said material being in the form of atriangular insert having concave sides complimentary to the convexcurvature of the sides of three adjacent cylindrical pellets, or beingintegrally formed as part of a special interstices-filling pellet, saidpellet being in the form of a six sided star with concave sidescomplimentary to the convex curvature of the sides of six adjacentcylindrical pellets, said pellets and material being bound and retainedin plate form by a solidified material, wherein said solidified materialand said plate material are elastic.

The teachings of all of these specifications are incorporated herein byreference.

As described and explained therein, an incoming projectile may contactthe pellet array in the plate in one of three ways:

1. Center contact. The impact allows the full volume of the pellet toparticipate in stopping the projectile, which cannot penetrate withoutpulverizing the whole pellet, an energy-intensive task.

2. Flank contact. The impact causes projectile yaw, thus makingprojectile arrest easier, as a larger frontal area is contacted, and notonly the sharp nose of the projectile. The projectile is deflectedsideways and needs to form for itself a large aperture to penetrate,thus allowing the armor to absorb the projectile energy,

3. Valley contact. The projectile is jammed, usually between the flanksof three pellets, all of which participate in projectile arrest. Thehigh side forces applied to the pellets are resisted by the pelletsadjacent thereto as held by the substrate or plate.

While the concept of valley contact is described as above in many of theaforementioned patents, it has now been discovered, and not previouslydescribed, that there are especially preferred parameters for suchvalley contact which significantly improve the properties of a compositearmor panel comprising an armor plate as defined above, which enhancethe ability of said composite armor panel to completely stop a pluralityof armor-piercing projectiles from penetrating said composite armorpanel.

In addition, it is to be noted that military authorities constantlychange their requirements for performance specifications of armor thatis ordered and the prior art does not teach or suggest the necessary orpreferred specifications for armor designed to deal with a specificpredetermined projectile threat.

Furthermore, said prior art does not teach or suggest the criticalparameters of the through-going valley nor the existence of a criticalratio between the diameter of the largest imaginary circle that fitswithin said through-going valley as defined above, and the length of apredetermined projectile, or the critical parameters of the ratio of thebody portion length of said pellets of the panel to the length of apredetermined projectile threat.

The term “high velocity projectiles” as used herein relates toprojectiles traveling at a speed of at least 700 m/sec.

In U.S. Pat. No. 6,112,635, and in an article by Ko and Song,“Characterization of Multifunctional Composite Armor”, pages 947-956(1996), ceramic spheres are described as being preferred. However it hasnow been discovered, according to the present invention, that ceramicpellets having the shape defined above, which can be tailored to meetthe challenge of a predetermined projectile threat, are superior tospherical pellets and serve to create a through-going valley of a lengthsufficient to effectively shatter a projectile since the flanks of thethree pellets bounding said valley all participate in the shattering ofthe projectile.

In especially preferred embodiments of the present invention saidceramic material is selected from the group consisting of aluminumoxide, silicon carbide, silicon nitride and boron carbide.

Preferably, said pellets have at least one circular cross-section.

In especially preferred embodiments of the present invention saidpellets are of round ended cylindrical shape,

Another advantage of the plate of the present invention is that inespecially preferred embodiments of the present invention,projectile-damaged pellets are removable from the plate and replaceableby intact pellets and matrix material for rapid repair and reuse of thecomposite armor plate.

In yet another preferred embodiment of the present invention saidpredetermined projectile threat is determined to be armor piercing 7.62mm projectiles, said pellet is of hexagonal cross-section with roundededges, as discussed above, and the ratio of body portion length to thelength of the predetermined projectile threat is between 0.17 and 0.26.

There are four main considerations concerning protective armor panels.The first consideration is weight. Protective armor for heavy but mobilemilitary equipment, such as tanks and large ships, is known. Such armorusually comprises a thick layer of alloy steel, which is intended toprovide protection against heavy and explosive projectiles. However,reduction of weight of armor, even in heavy equipment, is an advantagesince it reduces the strain on all the components of the vehicle.Furthermore, such armor is quite unsuitable for light vehicles such asautomobiles, jeeps, light boats, or aircraft, whose performance iscompromised by steel panels having a thickness of more than a fewmillimeters, since each millimeter of steel adds a weight factor of 7.8kg m².

Armor for light vehicles is expected to prevent penetration ofprojectiles, even when impacting at a speed in the range of 700 to 1000meters per second, or even faster. However, due to weight constraints itis difficult to protect light vehicles from high caliber armor-piercingprojectiles, e.g. of 12.7 and 14.5 mm and above, since the weight ofstandard armor to withstand such projectile is such as to impede themobility and performance of such vehicles.

A second consideration is cost. Overly complex armor arrangements,particularly those depending entirely on composite materials, can beresponsible for a notable proportion of the total vehicle cost, and canmake its manufacture non-profitable.

A third consideration in armor design is compactness. A thick armorpanel, including air spaces between its various layers, increases thetarget profile of the vehicle. In the case of civilian retrofittedarmored automobiles which are outfitted with internal armor, there issimply no room for a thick panel in most of the areas requiringprotection.

A fourth consideration relates to ceramic plates used for personal andlight vehicle armor, which plates have been found to be vulnerable todamage from mechanical impacts caused by rocks, falls, etc.

Fairly recent examples of armor systems are described in U.S. Pat. No.4,836,084, disclosing an armor plate composite including a supportingplate consisting of an open honeycomb structure of aluminum; and U.S.Pat. No. 4,868,040, disclosing an antiballistic composite armorincluding a shock-absorbing layer. Also of interest is U.S. Pat. No.4,529,640, disclosing spaced armor including a hexagonal honeycomb coremember.

Other armor plate panels are disclosed in British Patents 1,081,464;1,352,418; 2,272,272, and in U.S. Pat. No. 4,061,815 wherein the use ofsintered refractory material, as well as the use of ceramic materials,are described.

In the majority of the patents by the present inventor, the preferredpellets have a cylindrical body and at least one convexly curved endface and the especially preferred pellet is that described in U.S. Pat.No. 5,972,819 wherein the body is substantially cylindrical in shapewith at least one convexly curved end face, and preferably two identicalconvexly curved end faces, wherein the ratio D/R between the diameter Dof said cylindrical body and the radius R of curvature of said convexlycurved end faces is at least 0.64:1.

In EP1521051 there is described and claimed a composite armor plate forabsorbing and dissipating kinetic energy from high velocity projectiles,said plate comprising a single internal layer of pellets which are boundand retained in plate form by an elastic material, substantiallyinternally within said elastic material, such that the pellets are boundin a plurality of spaced apart rows and columns, said pellets being madeof ceramic material, and said pellets being substantially fully embeddedin the elastic material so that the pellets form an internal layer, saidpellets being characterized by a substantially regular geometriccross-sectional area, said cross-sectional area being substantiallypolygonal with rounded corners and wherein a majority of each of saidpellets is in direct contact with six adjacent pellets in the same layerto provide mutual lateral confinement therebetween.

In especially preferred embodiments of the present invention, there isused a plate as defined immediately above, wherein said pellets are ofhexagonal cross-section with substantially rounded corners as definedherein.

Ideally, in the current invention, the body portion of each ceramicpellet (other than the ceramic pellets at the edge of the ceramic pelletlayer) contacts the respective body portions of six adjacent pellets.However, in practice direct contact cannot always be achieved. It isknown that a ceramic body which has been pressed, by its nature, has anexternal surface area which is not smooth and has lack of consistency inits diameter along the main axis, and it is because of this that whencasting the panel with the solidified material, the casting material(s)(resin, molten aluminum, epoxy, and so on) seeps into spaces between theceramic bodies, including the very small spaces found between the wallsof two or more adjoining cylinders, forming a retaining substance inwhich the ceramic bodies are confined. Thus, even when the ceramicbodies are closely packed, the casting material will at least partiallypenetrate between them. This is due to the fact that during the pressingprocess, the ceramic material is compacted in the die and when thematerial is released from the die the material has a tendency to try andspring back to a less compact form. This generally occurs in the toppart of the material so pressed, which is the first part of the bodyreleased from the die. Thus, in this case, there will be a smalldifference in the diameter of the body along the vertical axis.Secondly, it is well known that during the pressing process there aresometimes differences in densification of the powder in different areasof the ceramic body. When sintering the ceramic body, these smalldifferences will cause the body to shrink in accordance with thedifferent compressions found in various areas of the body, resulting inanother reason for a “small” lack of homogeneity in the diameter alongthe vertical axis of the body. Thus there is rarely a situation in whichone ceramic body is perfectly in direct contact with a second ceramicbody in the panel, rather, the casting material will seep between thetwo bodies, at least partially encasing each of said bodies.

Furthermore, when the casting material of the plate is a liquefied solidmaterial, if one were to x-ray the panel, one would see that the panelshows a honey-combed shaped casting, which at least partially enclosesthe ceramic bodies.

The armor plates described in EP-A-0843149 and European PatentApplication 98301769.0 are made using ceramic pellets made substantiallyentirely of aluminum oxide. In WO-A-9815796 the ceramic bodies are ofsubstantially cylindrical shape having at least one convexly-curvedend-face, and are preferably made of aluminum oxide.

In WO 99/60327 it was described that the improved properties of theplates described in the earlier patent applications of this series is asmuch a function of the configuration of the pellets, which are ofregular geometric form with at least one convexly-curved end face (forexample, the pellets may be spherical or ovoidal, or of regulargeometric cross-section, such as hexagonal, with at least oneconvexly-curved end face), said panels and their arrangement as a singleinternal layer of pellets bound by an elastic solidified material,wherein each of a majority of said pellets is in direct contact with atleast four adjacent pellets and said curved end face of each pellet isoriented to substantially face in the direction of an outerimpact-receiving major surface of the plate. As a result, saidspecification teaches that composite armor plates superior to thoseavailable in the prior art can be manufactured using pellets made ofsintered refractory materials or ceramic materials having a specificgravity below that of aluminum oxide, e.g., boron carbide with aspecific gravity of 2.45, silicon carbide with a specific gravity of 3.2and silicon aluminum oxynitride with a specific gravity of about 3.2.

In preferred embodiments of the present invention said ceramic materialis selected from the group consisting of aluminum oxide silicon carbide,silicon nitride and boron carbide.

Thus, it was described in said publication that sintered oxides,nitrides, carbides and borides of magnesium, zirconium, tungsten,molybdenum, titanium, aluminum and silica can be used. Especiallypreferred for use in said publication and also for use in the ceramicinsert bodies of the present invention, is a ceramic material selectedfrom the group consisting of sintered oxide, nitrides, carbides andborides of aluminum, magnesium, zirconium, tungsten, molybdenum,titanium and silica although any suitable or newly discovered ceramicmaterial can be used for forming the inserts and insert pellets of thepresent invention.

All of these features are incorporated herein as preferred embodimentsof the present invention.

The solidified material can be any suitable material, such as aluminum,a thermoplastic polymer such as polycarbonate, or a thermoset plasticsuch as epoxy or polyurethane.

When aluminum is used as said solidified material an x-ray of the plateshows the formation of a honeycomb structure around the pellets. InFrench Patent 2,711,782, there is described a steel panel reinforcedwith ceramic materials; however said panel does not have the ability todeflect armor-piercing projectiles unless a thickness of about 8-9 mm ofsteel is used, which adds undesirable excessive weight to the panel andfurther backing is also necessary thereby further increasing the weightthereof.

The composite armor plate according to the present invention can be usedin conjunction with and as an addition to the standard steel platesprovided on armored vehicles or as add on armor for armored vehicleshaving aluminum or titanium containing rigid surfaces, as well as inconjunction with the laminated armor described and claimed in U.S. Pat.No. 6,497,966 the teachings of which are incorporated herein byreference.

According to a further aspect of the invention, there is provided amulti-layered armor panel, comprising an outer, impact-receiving layerformed by a composite armor plate as hereinbefore defined for deformingand shattering an impacting high velocity projectile; and an inner layeradjacent to said outer layer and, comprising a ballistic material forabsorbing the remaining kinetic energy from said fragments. Saidballistic material will be chosen according to cost and weightconsiderations and can be made of any suitable material such as Dyneema,Kevlar, aluminum, steel, titanium, or reinforced fiberglass.

As described, e.g., in U.S. Pat. No. 5,361,678, composite armor platecomprising a mass of spherical ceramic balls distributed in an aluminumalloy matrix is known in the prior art. However, such prior artcomposite armor plate suffers from one or more serious disadvantages,making it difficult to manufacture and less than entirely suitable forthe purpose of defeating metal projectiles. More particularly, in thearmor plate described in said patent, the ceramic balls are coated witha binder material containing ceramic particles, the coating having athickness of between 0.76 and 1.5 mm and being provided to help protectthe ceramic cores from damage due to thermal shock when pouring themolten matrix material during manufacture of the plate. However, thecoating serves to separate the harder ceramic cores of the balls fromeach other, and will act to dampen the moment of energy which istransferred and hence shared between the balls in response to an impactfrom a bullet or other projectile. Because of this and also because thematerial of the coating is inherently less hard than that of the ceramiccores, the stopping power of a plate constructed as described in saidpatent is not as good, weight for weight, as that of a plate inaccordance with the present invention and in which the ceramic pelletsare directly in contact with the solidified material.

The invention will now be described in connection with certain preferredembodiments with reference to the following illustrative figures so thatit may be more fully understood.

With reference now to the figures in detail, it is stressed that theparticulars shown are by way of example and for purposes of illustrativediscussion of the preferred embodiments of the present invention only,and are presented in the cause of providing what is believed to be themost useful and readily understood description of the principles andconceptual aspects of the invention. In this regard, no attempt is madeto show structural details of the invention in more detail than isnecessary for a fundamental understanding of the invention, thedescription taken with the drawings making apparent to those skilled inthe art how the several forms of the invention may be embodied inpractice.

In the drawings:

FIG. 1 is a perspective view, partially cut away, of a small section ofan armor plate according to the present invention;

FIGS. 2 a, is a side elevation of a ceramic pellet of the type used inthe armor plate of FIG. 1;

FIG. 2 b is a side elevation of a predetermined projectile to beprotected against by the armor plate of FIG. 1;

FIG. 2 c is a plan view from above of three ceramic pellets of the typeshown in FIG. 2 a and showing a valley between the three pellets; and

FIG. 3 is a view of a projectile undergoing shattering and fragmentationas a result of impact with a plate of the present invention.

Referring to FIG. 1, an exemplary armor plate consists of a plurality ofceramic pellets 2 which are embedded within a solidified material 4.

A ceramic pellet 2 of the type used in the armor plate shown in FIG. 1,is seen in more detail in FIG. 2 a. The ceramic pellet 2 shown in FIG. 2a has a cylindrical body portion 6 which has two planar opposite ends 8and a cylindrical surface 10. The body portion 6 has a length which isthe distance along the cylindrical axis between the two ends 8, andwhich is represented in FIG. 2 a by the letter H.

A respective convexly curved end portion 12 extends from each end 8 ofthe body portion 6. Each convexly curved end portion 12 has the form ofa segment of a sphere and has a base which lies adjacent to the bodyportion 6 and which has a diameter which is equal to the diameter of thebody portion 6.

Ceramic pellets 2 of the type described above are conveniently formed asa unitary body by pressing and methods for manufacturing such pelletsare well known in the art. The ceramic pellet 2 can be made from anysuitable ceramic material, and is preferably made from one of theceramic materials discussed above.

Looking again at FIG. 1, it can be seen that the ceramic pellets 2 arearranged in a single layer which is one pellet thick. The ceramicpellets 2 are arranged so that the cylindrical axes of the pellets 2 liesubstantially parallel to one another. In this case, each ceramic pellet2 has a respective convexly curved end portion 12 at each end.Accordingly, convexly curved end portions 12 are found at both sides ofthe armor plate. However, it will be appreciated that the ceramicpellets 2 need only have a single convexly curved end portion 12. Inthis case, the ceramic pellets 2 will be arranged so that the convexlycurved end portions 12 are located at one side of the armor plate, andthis side will be in impact receiving side of the armor plate.

As seen in FIG. 1, the ceramic pellets 2 are arranged so that each bodyportion 6 (other than the body portions 6 of the ceramic pellets 2 whichlie at the edge of the armor plate) is either in contact with, or liesclosely adjacent to the respective body portions 6 of six adjacentceramic pellets 2. As discussed above, whereas direct contact betweenthe body portions 6 is preferred, this cannot always be obtained inpractice. For those ceramic pellets 2 which lie at the edge of the armorplate, each body portion 6 lies in contact with, or closely adjacent tothe body portions of four adjacent ceramic pellets 2.

As seen in FIG. 1 and also in FIG. 2 c, a valley 14 is found betweeneach three adjacent ceramic pellets 2. The valleys 14 pass across thelayer of ceramic pellets. Referring to FIG. 2 c, each valley 14 has, incross section, a shape which is generally triangular, with each side ofthe triangle being concavely curved. This is because, of course, eachvalley 14 is formed between the cylindrical surfaces 10 of the bodyportions 6 of the three adjacent ceramic pellets 2. Of course, where thebody portions 6 of the ceramic pellets 2 are not cylindrical in shape,then the valleys 14 will have different shapes.

For the purposes of the current invention, it is important to quantifythe size of the valleys 14—bearing in mind that the shape of the valleys14 can vary depending upon the shape of the body portions 6 of theceramic pellets 2. For present purposes, the size of each valley 14 isdefined with respect to the largest imaginary circle 16 which can fitwithin the valley 14, between the neighboring body portions 6, and lyingsubstantial perpendicularly to the axes of the neighboring body portions6. Such an imaginary circle 16, having a diameter d, is shown in thevalley 14 in FIG. 2 c.

As shown in FIG. 1, the ceramic pellets 2 are embedded in a solidifiedmaterial 4, which can be any suitable solidified material, and ispreferably one of the solidified materials mentioned above. Thesolidified material 4 passes through the valleys 14 and covers theceramic pellets 2 on either side of the armor plate. As discussed above,the solidified material is generally slightly elastic so that when thearmor plate is impacted by a projectile, the armor plate flexesslightly.

The armor plate is tailored to be particularly effective against a 7.62mm caliber projectile 18 having a predetermined projectile length. Asseen in FIG. 2 b, the projectile length is the entire length of theprojectile 16 (but not including any casing).

As discussed above, it has been found that when the size and shape ofthe ceramic pellets 2 are chosen so as to give the body portion length Hand the diameter d of the largest imaginary circle 16 specificdimensions relative to the projectile 18, the armor plate isparticularly effective at protecting against a projectile 18 of thatlength. Hence, for any particular projectile length, the size and shapeof the ceramic pellets 2 should ideally be chosen so that the bodyportion length is from 17% to 29% of the projectile length, and thediameter of the largest imaginary circle 16 is from 6% to 10% of theprojectile length.

By way of example, when the projectile length is 35 mm, the body portionlength may be from 5.95 mm to 10.15 mm, and the diameter of the largestimaginary circle 16 may be from 2.1 mm to 3.5 mm. It is also possible tocalculate the body portion length and the diameter of the largestimaginary circle 16 based on an anticipated range of projectile length.For example, when the projectile length is anticipated to be from 32.8mm to 37 mm, the diameter of the largest imaginary circle 16 will befrom 1.96 mm to 3.70 mm, and the body portion length will be form 5.57mm to 10.73 mm.

The armor plate is used to protect against a projectile of thepre-determined length. The armor plate absorbs and dissipates kineticenergy from the projectile, and the projectile is shattered intofragments. It will be noted that the armor plate does not necessarilyprevent penetration of the projectile on its own. The armor plate willgenerally be used in combination with the second layer, as discussedabove. The second layer serves to catch and retain fragments of theprojectile and to absorb the remaining kinetic energy of the fragments.

It will be evident to those skilled in the art that the invention is notlimited to the details of the foregoing illustrative embodiments andthat the present invention may be embodied in other specific forms. Thepresent embodiments are therefore to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription.

1. An armor plate for absorbing and dissipating kinetic energy fromarmor piercing 7.62 mm projectiles having a projectile length of from32.8 mm to 37 mm, the armor plate comprising a plurality of ceramicpellets and a solidified material, each ceramic pellet having a bodyportion and a convexly curved end portion, each body portion having twoopposite ends, an axis passing through each end and a substantiallyconstant cross-section along said axis, and each convexly curved endportion extending from an end of the corresponding body portion, eachbody portion having a body portion length along said axis between thetwo ends, the ceramic pellets being embedded in the solidified materialso that the solidified material retains the ceramic pellets in a ceramicpellet layer which is one pellet thick with said convexly curved endportions lying at or adjacent an impact receiving side of the armorplate, wherein the ceramic pellet layer is the only layer of ceramicpellets in the armor plate, wherein the ceramic pellet layer has an edgeextending therearound formed by a subset of said ceramic pellets,wherein said ceramic pellets are arranged so that the body portion ofsubstantially each pellet, other than of the pellets of said subset,lies in contact with or closely adjacent to the respective body portionsof six neighboring ones of the ceramic pellets so that there are aplurality of valleys extending through the ceramic pellet layer witheach valley being bordered by three adjacent ceramic pellets, whereinsubstantially each valley has a shape and size such that the diameter ofthe largest imaginary circle that will fit into said each valley betweenthe neighboring body portions and substantially perpendicularly to theneighboring axes is from 1.96 mm to 3.7 mm, and wherein each bodyportion length is from 5.57 mm to 10.73 mm.
 2. An armor plate accordingto claim 1, wherein the diameter of the largest imaginary circle is from1.96 mm to 3.40 mm and each body portion length is from 5.57 mm to 9.86mm; or wherein the diameter of the largest imaginary circle is from 2.04mm to 3.50 mm and each body portion length is from 5.78 mm to 10.15 mm;or wherein the diameter of the largest imaginary circle is from 2.10 mmto 3.60 mm and each body portion length is from 5.95 mm to 10.44 mm; orwherein the diameter of the largest imaginary circle is from 2.16 mm to3.70 mm and each body portion length is from 6.12 mm to 10.73 mm.
 3. Amethod of manufacturing an armor plate for absorbing and dissipatingkinetic energy from armor piercing 7.62 mm projectiles having apredetermined projectile length, comprising: selecting said projectilelength of said armor piercing 7.62 mm projectiles for which the kineticenergy is to be absorbed and dissipated by said armor plate;manufacturing the armor plate wherein the armor plate comprises aplurality of ceramic pellets and a solidified material, each ceramicpellet having a body portion and a convexly curved end portion, eachbody portion having two opposite ends, an axis passing through each endand a substantially constant cross-section along said axis, and eachconvexly curved end portion extending from an end of the correspondingbody portion, each body portion having a body portion length along saidaxis between the two ends, the ceramic pellets being embedded in thesolidified material so that the solidified material retains the ceramicpellets in a ceramic pellet layer which is one pellet thick with saidconvexly curved end portions lying at or adjacent an impact receivingside of the armor plate, wherein the ceramic pellet layer is the onlylayer of ceramic pellets in the armor plate, wherein said ceramic pelletlayer has an edge extending therearound formed by a subset of saidceramic pellets, wherein said ceramic pellets are arranged so that thebody portion of substantially each pellet, other than of the pellets ofsaid subset, lies in contact with or closely adjacent to the respectivebody portions of six neighboring ones of the ceramic pellets so thatthere are a plurality of valleys extending through the ceramic pelletlayer with each valley being bordered by three adjacent ceramic pellets;wherein said manufacture includes selecting the size and shape of theceramic pellets according to the predetermined projectile length so thatsubstantially each valley has a shape and size such that the diameter ofthe largest imaginary circle that will fit into said each valley betweenthe neighboring body portions and substantially perpendicularly to theneighboring axes is from 6% to 10% of the predetermined projectilelength, and wherein each body portion length is from 17% to 29% of thepredetermined projectile length.
 4. A method of using an armor plate,said method comprising: providing an armor plate comprising a pluralityof ceramic pellets and a solidified material, each ceramic pellet havinga body portion and a convexly curved end portion, each body portionhaving two opposite ends, an axis passing through each end and asubstantially constant cross-section along said axis, and each convexlycurved end portion extending from an end of the corresponding bodyportion, each body portion having a body portion length along said axisbetween the two ends, the ceramic pellets being embedded in thesolidified material so that the solidified material retains the ceramicpellets in a ceramic pellet layer which is one pellet thick with saidconvexly curved end portions lying at or adjacent an impact receivingside of the armor plate, wherein the ceramic pellet layer is the onlylayer of ceramic pellets in the armor plate, wherein said ceramic pelletlayer has an edge extending therearound formed by a subset of saidceramic pellets, wherein said ceramic pellets are arranged so that thebody portion of substantially each pellet, other than of the pellets ofsaid subset, lies in contact with or closely adjacent to the respectivebody portions of six neighboring ones of the ceramic pellets so thatthere are a plurality of valleys extending through the ceramic pelletlayer with each valley being bordered by three adjacent ceramic pellets;Using said composite armor plate for absorbing and dissipating kineticenergy from armor piercing 7.62 mm projectiles having a predeterminedprojectile length; and Wherein substantially each valley has a shape andsize such that the diameter of the largest imaginary circle that willfit into said each valley between the neighboring body portions andsubstantially perpendicularly to the neighboring axes is from 6% to 10%of the predetermined projectile length, and wherein each body portionlength is from 17% to 29% of the predetermined projectile length.
 5. Amethod according to claim 3, wherein the armor piercing projectile has atungsten carbide core and the diameter of the largest imaginary circleis from 7% to 9% of the predetermined projectile length.
 6. A methodaccording to claim 4, wherein the armor piercing projectile has atungsten carbide core and the diameter of the largest imaginary circleis from 7% to 9% of the predetermined projectile length.
 7. A methodaccording to claim 3, wherein the armor piercing projectile has atungsten carbide core and each body portion length is from 22% to 29% ofthe predetermined projectile length.
 8. A method according to claim 3,wherein each body portion length is from 19% to 24% of the predeterminedprojectile length.
 9. An armor plate or method according to claim 1,wherein the ceramic pellets are substantially internal within thesolidified material and the outer faces of the armor plate aresubstantially formed by the solidified material.
 10. An armor plate ormethod according to claim 1, wherein the body portion of each ceramicpellets has a maximum cross-sectional dimension of greater than 13 mm,and preferably between 14 mm and 20 mm.
 11. An armor plate or methodaccording to claim 1, wherein each ceramic pellet has an overall lengthalong said axis of between 11.6 mm and 17 mm.
 12. An armor plate ormethod according to claim 1, wherein the diameter of said largestimaginary circle is no greater than 3 mm.
 13. An armor plate or methodaccording to claim 1, wherein the shape of the body portion of eachceramic pellet is either circular cylindrical, or generally hexagonalwith rounded edges between each pair of adjacent axially extendingfaces.
 14. A multi-layered armor panel comprising an armor plateaccording to claim 1, said armor plate forming an outer layer fordeforming and shattering into fragments an impacting high-velocity armorpiercing projectile, and a second layer positioned inwardly of andadjacent to the armor plate, the second layer comprising a material thatis softer than the ceramic pellets and the second layer capturing thefragments and absorbing the remaining kinetic material from thefragments.
 15. A multi-layered armor panel according to claim 14,wherein the second layer is made of: polyethylene with an ultra highmolecular weight; aramid; aluminium; steel; titanium; or reinforcedfiberglass.
 16. A multi-layered armor panel according to claim 14,further comprising a third layer positioned inwardly of the second layerand made of aluminium.